The present invention relates to archery bows, and particularly to improvements of the attachment of bow strings and cables to the force-multiplying eccentric cams or wheels of a compound bow.
Compound bows are described in Allen U.S. Pat. No 3,486,495. In a compound bow the ends of opposite ends of limbs of the bow are drawn together partly by the action of flexible tension-bearing members, usually steel cables, being wound on eccentric cams or wheels, etc., hereinafter generally called eccentric devices, which are rotated by the action of drawing the bow. As the bow is drawn, extension portions of the bowstring are unwound from around a portion of each of the eccentric devices, rotating them about respective axes of rotation which are located at the tips of the limbs of the bow, oriented perpendicular to the plane of the bow string and bow. This causes the cables to be wound onto the eccentric devices. Since the cables and bowstring both act to pull the tips of the opposite limbs toward each other, both the cables and the bowstring need to be securely attached to the eccentric devices. Previously, the cables have extended around each eccentric device and a "pigtail" end of each cable has extended from the eccentric device, with a fitting being attached to the end of the pigtail to receive the looped end of a bowstring, usually made of a more elastic fiber. The bowstring is fastened to the end of the cable extending from the eccentric device at each end of the bow and is thus relatively easily exchangeable when it has become worn. However, there is some hazard associated with this manner of attachment of the bowstring, since the portion of the cable between the eccentric device and the bowstring is the portion of the cable which receives the highest stresses and the greatest amount of flexure and twisting. As a result, this portion of the cable is most frequently subject to failure during use of a compound bow. Particularly when a compound bow of high power is being used to cast arrows of relatively light weight, the sudden stresses occurring as the bowstring reaches its final position and the arrow leaves the bow may result in dangerous breakage, with the teardrop-shaped bowstring attachment member being carried away by the bowstring as it elastically contracts, making the attachment member and any attached piece of cable into a dangerous flail or projectile.
Another disadvantage of the use of such a steel cable pigtail is that since such a pigtail of steel cable is somewhat heavier than other materials which could be used, the mass of the length of the steel cable pigtail, and that of the bow string attachment teardrops or other similar devices, are greater contributions to the total inertia of the bow than is desired. Bow performance, then, could be improved by the ability to replace the steel cable pigtails and the swaged-on bowstring attachments, if a practical method of attachment of the bowstring directly to the eccentric device is made available.
A problem in the past, however, has been that it has not been known how to attach an end of a cable or bowstring securely enough to an eccentric device to be safe in use, where the possibility of loosening creates a serious risk of injury to the user of the compound bow, because of the greater tension forces involved, and because of the greater amounts of shock encountered, particularly by the bowstring.
What is desired, then, is an improved, safer, compound bow in which the cables and the bowstring are attached securely to the eccentric cam or wheels, without the need for a pigtail and its included hook or the like, and in which the cables and bowstring are adjustable and replaceable with reasonable ease.